Lewy bodies are located preferentially in limbic areas in diffuse Lewy body disease

Alteration of medial temporal lobe metabolism related to Alzheimer's disease and dementia with lewy bodies

BACKGROUND

Association of medial temporal lobe (MTL) metabolism with Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) has not been evaluated considering their mixed disease (MD).

METHODS

131 patients with AD, 133 with DLB, 122 with MD, and 28 normal controls (NCs) underwent neuropsychological tests, assessments for parkinsonism, cognitive fluctuation (CF), and visual hallucinations (VH), and 18F-fluorodeoxyglucose PET to quantify MTL metabolism in the amygdala, hippocampus, and entorhinal cortex. The effects of AD and DLB on MTL metabolism were evaluated using general linear models (GLMs). Associations between MTL metabolism, cognition, and clinical features were evaluated using GLMs or logistic regression models separately performed for the AD spectrum (NC + AD + MD), DLB spectrum (NC + DLB + MD), and disease groups (AD + DLB + MD). Covariates included age, sex, and education.

RESULTS

AD was associated with hippocampal/entorhinal hypometabolism, whereas DLB was associated with relative amygdalar/hippocampal hypermetabolism. Relative MTL hypermetabolism was associated with lower attention/visuospatial/executive scores and severe parkinsonism in both the AD and DLB spectra and disease groups. Left hippocampal/entorhinal hypometabolism was associated with lower verbal memory scores, whereas right hippocampal hypometabolism was associated with lower visual memory scores in both the AD spectrum and disease groups. Relative MTL hypermetabolism was associated with an increased risk of CF and VH in the disease group, and relative amygdalar hypermetabolism was associated with an increased risk of VH in the DLB spectrum.

CONCLUSIONS

Entorhinal-hippocampal hypometabolism and relative amygdala-hippocampal hypermetabolism could be characteristics of AD- and DLB-related neurodegeneration, respectively.

Regional differences in the link between water exchange rate across the blood-brain barrier and cognitive performance in normal aging

The blood-brain barrier (BBB) undergoes functional changes with aging which may contribute to cognitive decline. A novel, diffusion prepared arterial spin labeling-based MRI technique can measure the rate of water exchange across the BBB (kw) and may thus be sensitive to age-related alterations in water exchange at the BBB. However, studies investigating relationships between kw and cognition have reported different directions of association. Here, we begin to investigate the direction of associations between kw and cognition in different brain regions, and their possible underpinnings, by evaluating links between kw, cognitive performance, and MRI markers of cerebrovascular dysfunction and/or damage. Forty-seven healthy older adults (age range 61-84) underwent neuroimaging to obtain whole-brain measures of kw, cerebrovascular reactivity (CVR), and white matter hyperintensity (WMH) volumes. Additionally, participants completed uniform data set (Version 3) neuropsychological tests of executive function (EF) and episodic memory (MEM). Voxel-wise linear regressions were conducted to test associations between kw and cognitive performance, CVR, and WMH volumes. We found that kw in the frontoparietal brain regions was positively associated with cognitive performance but not with CVR or WMH volumes. Conversely, kw in the basal ganglia was negatively associated with cognitive performance and CVR and positively associated with regional, periventricular WMH volume. These regionally dependent associations may relate to different physiological underpinnings in the relationships between kw and cognition in neocortical versus subcortical brain regions in older adults.

Neuroglial Senescence, α-Synucleinopathy, and the Therapeutic Potential of Senolytics in Parkinson’s Disease

Parkinson’s disease (PD) is the most common movement disorder and the second most prevalent neurodegenerative disease after Alzheimer’s disease. Despite decades of research, there is still no cure for PD and the complicated intricacies of the pathology are still being worked out. Much of the research on PD has focused on neurons, since the disease is characterized by neurodegeneration. However, neuroglia has become recognized as key players in the health and disease of the central nervous system. This review provides a current perspective on the interactive roles that α-synuclein and neuroglial senescence have in PD. The self-amplifying and cyclical nature of oxidative stress, neuroinflammation, α-synucleinopathy, neuroglial senescence, neuroglial chronic activation and neurodegeneration will be discussed. Finally, the compelling role that senolytics could play as a therapeutic avenue for PD is explored and encouraged.

Dementia-related psychosis and the potential role for pimavanserin

Dementia-related psychosis (DRP) is prevalent across dementias and typically manifests as delusions and/or hallucinations. The mechanisms underlying psychosis in dementia are unknown; however, neurobiological and pharmacological evidence has implicated multiple signaling pathways and brain regions. Despite differences in dementia pathology, the neurobiology underlying psychosis appears to involve dysregulation of a cortical and limbic pathway involving serotonergic, gamma-aminobutyric acid ergic, glutamatergic, and dopaminergic signaling. Thus, an imbalance in cortical and mesolimbic excitatory tone may drive symptoms of psychosis. Delusions and hallucinations may result from (1) hyperactivation of pyramidal neurons within the visual cortex, causing visual hallucinations and (2) hyperactivation of the mesolimbic pathway, causing both delusions and hallucinations. Modulation of the 5-HT2A receptor may mitigate hyperactivity at both psychosis-associated pathways. Pimavanserin, an atypical antipsychotic, is a selective serotonin inverse agonist/antagonist at 5-HT2A receptors. Pimavanserin may prove beneficial in treating the hallucinations and delusions of DRP without worsening cognitive or motor function.

Neural Correlates of Cognitive Performance in Alzheimer's Disease- and Lewy Bodies-Related Cognitive Impairment

BACKGROUND

Clinicopathological studies have demonstrated that the neuropsychological profiles and outcomes are different between two dementia subtypes, namely Alzheimer's disease (AD) and Lewy bodies-related disease.

OBJECTIVE

We investigated the neural correlates of cognitive dysfunction in patients with AD-related cognitive impairment (ADCI) and those with Lewy bodies-related cognitive impairment (LBCI).

METHODS

We enrolled 216 ADCI patients, 183 LBCI patients, and 30 controls. Cortical thickness and diffusion tensor imaging analyses were performed to correlate gray matter and white matter (WM) abnormalities to cognitive composite scores for memory, visuospatial, and attention/executive domains in the ADCI spectrum (ADCI patients and controls) and the LBCI spectrum (LBCI patients and controls) separately.

RESULTS

Memory dysfunction correlated with cortical thinning and increased mean diffusivity in the AD-prone regions, particularly the medial temporal region, in ADCI. Meanwhile, it only correlated with increased mean diffusivity in the WM adjacent to the anteromedial temporal, insula, and basal frontal cortices in LBCI. Visuospatial dysfunction correlated with cortical thinning in posterior brain regions in ADCI, while it correlated with decreased fractional anisotropy in the corpus callosum and widespread WM regions in LBCI. Attention/executive dysfunction correlated with cortical thinning and WM abnormalities in widespread brain regions in both disease spectra; however, ADCI had more prominent correlation with cortical thickness and LBCI did with fractional anisotropy values.

CONCLUSIONS

Our study demonstrated that ADCI and LBCI have different neural correlates with respect to cognitive dysfunction. Cortical thinning had greater effects on cognitive dysfunction in the ADCI, while WM disruption did in the LBCI.

The Amygdala as a Locus of Pathologic Misfolding in Neurodegenerative Diseases

Over the course of most common neurodegenerative diseases the amygdala accumulates pathologically misfolded proteins. Misfolding of 1 protein in aged brains often is accompanied by the misfolding of other proteins, suggesting synergistic mechanisms. The multiplicity of pathogenic processes in human amygdalae has potentially important implications for the pathogenesis of Alzheimer disease, Lewy body diseases, chronic traumatic encephalopathy, primary age-related tauopathy, and hippocampal sclerosis, and for the biomarkers used to diagnose those diseases. Converging data indicate that the amygdala may represent a preferential locus for a pivotal transition from a relatively benign clinical condition to a more aggressive disease wherein multiple protein species are misfolded. Thus, understanding of amygdalar pathobiology may yield insights relevant to diagnoses and therapies; it is, however, a complex and imperfectly defined brain region. Here, we review aspects of amygdalar anatomy, connectivity, vasculature, and pathologic involvement in neurodegenerative diseases with supporting data from the University of Kentucky Alzheimer's Disease Center autopsy cohort. Immunohistochemical staining of amygdalae for Aβ, Tau, α-synuclein, and TDP-43 highlight the often-coexisting pathologies. We suggest that the amygdala may represent an "incubator" for misfolded proteins and that it is possible that misfolded amygdalar protein species are yet to be discovered.

Fluorescence and autoradiographic evaluation of tau PET ligand PBB3 to α-synuclein pathology

BACKGROUND

The tau PET ligand 2-((1E,3E)-4-(6-([¹¹ C]methylamino)pyridin-3-yl)buta-1,3-dienyl)benzo[d]thiazol-6-ol ([¹¹ C]PBB3) binds to a wide range of tau pathology; however, binding property of PBB3 to non-tau inclusions remains unknown. To clarify whether [¹¹ C]PBB3 binds to α-synuclein pathology, reactivity of PBB3 was assessed by in vitro fluorescence and autoradiographic labeling of brain sections from α-synucleinopathies patients.

METHOD

Of 10 pure Lewy body disease and 120 multiple system atrophy (MSA) cases in the Mayo Clinic brain bank, we selected 3 Lewy body disease and 4 MSA cases with a range of α-synuclein severity based on the quantitative analysis of α-synuclein burden. PBB3 fluorescence labeling, double or single immunostaining for α-synuclein and phospho-tau, Prussian blue staining, and in vitro autoradiography with [¹¹ C]PBB3 were performed for these selected samples.

RESULTS

PBB3 fluorescence labeled various α-synuclein lesions including Lewy bodies, Lewy neurites, spheroids, glial cytoplasmic inclusions, and neuronal cytoplasmic inclusions. Meanwhile, autoradiographic labeling with [¹¹ C]PBB3 at 10 nM demonstrated no significant binding in Lewy body disease cases. In contrast, significant autoradiographic binding of [¹¹ C]PBB3 to the striatopallidal fibers was found in 2 MSA cases, which had high densities of glial cytoplasmic inclusions without tau or iron deposits in this region.

CONCLUSIONS

Given that the maximum concentration of [¹¹ C]PBB3 in human PET scans is approximately 10 nM, the present data imply that α-synuclein pathology in Lewy body disease is undetectable by [¹¹ C]PBB3-PET, whereas those in a subset of MSA cases with high densities of glial cytoplasmic inclusions could be captured by this radioligand. © 2017 International Parkinson and Movement Disorder Society.

Clinical and neuropathological features of dementia with Lewy bodies

Dementia with Lewy bodies (DLB) is an increasingly recognized entity which overlaps in clinical, pathological and genetic features with Alzheimer's (AD) and Parkinson's disease (PD). Clinically, it is characterized by progressive cognitive impairment with significant fluctuations in alertness, parkinsonism, and psychosis with recurrent hallucinations. The neuropathological hallmarks are the intracytoplasmic inclusions in substantia nigra typical of PD, known as Lewy bodies (LB), but widely distributed throughout paralimbic and neocortical regions. Most of the cases also coexist with a plaque predominant AD. The evidence of alpha-synuclein in LB and related neurites as well as of a synuclein fragment in AD plaques opens new links among these neurodegenerative diseases. This article will review briefly the clinical and pathologicalfeatures that DLB shares with AD and PD, as well as those that support the idea that it is a distinct disorder.

Visual Perceptual Organization Ability in Autopsy-Verified Dementia with Lewy Bodies and Alzheimer's Disease

OBJECTIVES

Prominent impairment of visuospatial processing is a feature of dementia with Lewy bodies (DLB), and diagnosis of this impairment may help clinically distinguish DLB from Alzheimer's disease (AD). The current study compared autopsy-confirmed DLB and AD patients on the Hooper Visual Organization Test (VOT), a test that requires perceptual and mental reorganization of parts of an object into an identifiable whole. The VOT may be particularly sensitive to DLB since it involves integration of visual information processed in separate dorsal and ventral visual "streams".

METHODS

Demographically similar DLB (n=28), AD (n=115), and normal control (NC; n=85) participants were compared on the VOT and additional neuropsychological tests. Patient groups did not differ in dementia severity at time of VOT testing. High and Low AD-Braak stage DLB subgroups were compared to examine the influence of concomitant AD pathology on VOT performance.

RESULTS

Both patient groups were impaired compared to NC participants. VOT scores of DLB patients were significantly lower than those of AD patients. The diagnostic sensitivity and specificity of the VOT for patients versus controls was good, but marginal for DLB versus AD. High-Braak and low-Braak DLB patients did not differ on the VOT, but High-Braak DLB performed worse than Low-Braak DLB on tests of episodic memory and language.

CONCLUSIONS

Visual perceptual organization ability is more impaired in DLB than AD but not strongly diagnostic. The disproportionate severity of this visual perceptual deficit in DLB is not related to degree of concomitant AD pathology, which suggests that it might primarily reflect Lewy body pathology. (JINS, 2016, 22, 609-619).

Olfaction deterioration in cognitive disorders in the elderly

BACKGROUND

Parkinson's and Alzheimer's diseases are widespread neurodegenerative pathologies. Parkinson's disease affects about 1 % of the population over the age of 65 years, while Alzheimer is considered the most common cause of dementia, with an annual incidence of 1 % in persons aged 65 years. It has been demonstrated that both these neurodegenerative diseases are associated with smell dysfunction.

AIM

The aim of the present review is to describe briefly modern olfactory evaluation tools as well as the importance of olfactory sensitivity screening in the elderly, especially where cognitive disorders, such as Alzheimer's or Parkinson's diseases, are suspected.

METHODS

A brief literature review focusing on the basic principle of smell tests is illustrated together with their application in elderly patients affected by cognitive disorders, in particular Parkinson's and Alzheimer's diseases.

RESULTS/CONCLUSIONS

Alzheimer's and Parkinson's diseases are both neurodegenerative disorders typically found in the elderly. As both diseases are characterized by the early presence of dysosmia, simple validated smell tests could very well help clinicians in the early diagnosis of these neuropathological conditions. Elderly patients complaining of smell loss and found to be dysosmic, by means of validated olfactory tests, should be neurologically evaluated as early as possible to detect slight motor abnormalities in an at-risk population.

Theory of Mind in normal ageing and neurodegenerative pathologies

This paper reviews findings in three subcomponents of social cognition (i.e., Theory of Mind, facial emotion recognition, empathy) during ageing. Changes over time in social cognition were evaluated in normal ageing and in patients with various neurodegenerative pathologies, such as Alzheimer's disease, mild cognitive impairment, frontal and temporal variants of frontotemporal lobar degeneration and Parkinson's disease. Findings suggest a decline in social cognition with normal ageing, a decline that is at least partially independent of a more general cognitive or executive decline. The investigation of neurodegenerative pathologies showing specific deficits in Theory of Mind in relation to damage to specific cerebral regions led us to suggest a neural network involved in Theory of Mind processes, namely a fronto-subcortical loop linking the basal ganglia to the regions of the frontal lobes.

Seizures in corticobasal degeneration: a case report

Seizures are relatively common in Alzheimer disease (AD) and other neurodegenerative disorders. To our knowledge, however, there have been no reports of seizures associated with corticobasal degeneration (CBD). We describe a patient with brain biopsy features suggestive of CBD whose course was complicated by complex partial seizures with secondary generalization. Thus, the occurrence of seizures in a patient with dementia should not exclude the diagnosis of CBD.

Alzheimer disease with amygdala Lewy bodies: a distinct form of alpha-synucleinopathy

Lewy bodies (LBs) are alpha-synuclein-immunoreactive neuronal inclusions with a predilection for specific cortical and subcortical regions, including the amygdala. In this study, the presence of LBs was assessed in 347 cases of Alzheimer disease (AD). In 87 cases, LB pathology was diagnostic of brainstem (n=3), transitional (n=32), or diffuse (n=52) Lewy body disease (LBD). The remaining 260 cases of AD were screened for amygdala LBs (AD/ALB) and 62 (24%) cases were found. If AD/LBD cases are included, LBs were detected in 149 (43%) cases of AD. The presence alpha-synuclein pathology was assessed in multiple brain regions of the 62 cases of AD/ALB and 57 randomly selected cases of AD, and only sparse alpha-synuclein pathology was detected in both. The burden of alpha-synuclein pathology in brainstem nuclei, amygdala, and neocortex was significant lower in AD/ALB than in AD/LBD. In comparison to AD/LBD, AD/ALB did not differ in age at death, disease duration, male-to-female ratio, brain weight, Braak neurofibrillary tangle stage, average senile plaque density, or apolipoprotein E epsilon4 allele frequency. The results suggest that AD/ALB is pathologically different from AD/LBD, suggesting that it is a neuropathologically distinct and isolated alpha-synucleinopathy.

Investigation of Lewy pathology in the visual pathway of brains of dementia with Lewy bodies

We examined 19 autopsied cases of dementia with Lewy bodies (DLB) using pathological and alpha-synuclein-immunohistochemical methods, and investigated Lewy pathology in the primary visual pathway (lateral geniculate body and Brodmann's area 17), secondary visual pathway (pulvinar, Brodmann's areas 18 and 19, and inferior temporal cortex), amygdala and substantia nigra, to clarify the relationship between visual misidentification and Lewy pathology in the visual pathway. Consequently, the secondary visual pathway revealed significantly severer Lewy pathology than the primary visual pathway, suggesting that the degeneration of the secondary visual pathway induces dysfunction in the recognition of objects shape and color. In addition, the amygdala revealed significantly severer Lewy pathology and neuronal loss than the primary and secondary visual pathways, suggesting that the degeneration of the amygdala, which receives the afferent connections from the substantia nigra, fails to modulate the visual processing according to cognition and emotion. These findings suggest that Lewy pathologies in the secondary visual pathway and amygdala may cause the dysfunction of the visuo-amygdaloid pathway and participate in visual misidentification in DLB patients. In addition, we compared Lewy pathology between cases with and without visual hallucinations, and showed no significant differences between the two groups.

Characteristics of alpha-synucleinopathy in centenarians

To investigate the characteristics of alpha-synucleinopathy in the brains of centenarians, the autopsied brains and spinal cords from 23 cases were studied. Coronal slices were prepared from a section of the cerebral hemisphere, following the guidelines of the Consortium to Establish a Registry for Alzheimer's Disease (AD) (CERAD) and the consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB). Spinal cord specimens were prepared at each segment from the third cervical to the third sacral segment. In all cases, we performed standard stainings of hematoxylin-eosin, Klüver-Barrera, and Gallyas-Braak combined with Luxol fast blue/cresyl violet, and alpha-synuclein (AS), phosphorylated tau (AT8) and beta-amyloid protein immunostainings. One-way ANOVA analysis, Chi-square or Fisher exact test were used for statistical analysis. Overall, AS-positive structures were found in 8 (34.8%) of our 23 centenarians, 6 (35.3%) of 17 demented patients, and four (40%) out of ten AD patients. The frequencies of AS lesions in the brains with senile plaque (SP) stage 0-A, B, and C were 27.7, 33, and 50%, respectively. No statistical differences were found among the frequencies of AS lesions in the subgroups of NFT stages I-II, III-IV, and V-VI (P=0.478). Most cases showed a widespread distribution of AS-positive structures except for one patient, in whose brain only the medulla was involved. The distribution pattern of AS-positive lesions was similar to that in Parkinson's disease or DLB, but the pigmented neurons in substantia nigra were relatively well preserved. Our findings indicate that there is a high frequency of alpha-synucleinopathy in centenarians, SP-positive and AS-positive lesions may involve a synergistic interaction.

Lewy bodies in Alzheimer's disease: a neuropathological review of 145 cases using alpha-synuclein immunohistochemistry

Antibodies to alpha-synuclein (AS) now provide a sensitive and specific method for the detection of Lewy bodies (LBs) and their use will allow a more accurate determination of the prevalence of LBs in Alzheimer's Disease (AD). Studies using AS immunohistochemistry (IHC) have found LBs in the amygdala of over 60% early onset familial AD and in 50% of Down's syndrome patients with AD, however, no studies have reported the use of AS IHC to detect LBs in a large cohort of sporadic AD. This study examined 145 sporadic AD cases diagnosed using CERAD criteria from 1995-1999 for the presence of LBs using AS IHC. AS IHC detected LBs in 88/145 (60.7%) of sporadic AD cases. Similarly, LBs were found in 56.8% of the 95 cases fulfilling the more stringent NIA-RI criteria for the diagnosis of AD (Braak stage 5-6). In all cases with LBs, the amygdala was involved and LBs were always most numerous in this area, however, in some cases LBs in the substantia nigra were rare or not present. In conclusion, this study found that AS IHC detects LBs in the majority of sporadic AD cases and that the amygdala is the most commonly affected region.

The distribution pattern of pathology and cholinergic deficits in amygdaloid complex in Alzheimer's disease and dementia with Lewy bodies

We studied the distribution pattern of pathology and cholinergic deficits in the subnuclei of the amygdaloid complex (AC) in five patients with Alzheimer's disease (AD), eight with dementia with Lewy bodies (DLB) and five normal controls. In controls, the basal nucleus contained the highest choline acetyltransferase activity; the activity in the lateral and central nuclei and those in the cortical, medial and accessory basal nuclei were comparable. In AD, there was a significant decrease in choline acetyltransferase activity in the accessory basal and lateral nuclei, in DLB a significant decrease was observed in the accessory basal, lateral and cortical nuclei. Compared to controls the hyperphosphorylated tau-pathology burden was significantly higher in the basal, central and medial nuclei in AD and in the central, cortical, lateral and medial nuclei in DLB. The amyloid plaque burden was significantly higher in the accessory basal, basal, lateral and cortical nuclei in AD and in all nuclei in DLB. The alpha-synuclein burden was significantly higher in all nuclei in both AD and DLB. Compared to AD alpha-synuclein burden was higher in all nuclei in DLB. There were no correlations between the distribution pattern of hyperphosphorylated tau-pathology, amyloid plaques and alpha-synuclein-positive structures, and choline acetyltransferase activity, except the lateral nucleus in DLB. In conclusion we found no relationship between the pattern of cholinergic deficits and the distribution pattern of lesions in the AC of patients with AD or DLB. Cholinergic deficits were more prominent in the nuclei of basolateral (BL) group in AD, whereas the nuclei of both BL and corticomedial groups were involved in DLB, which may be due to the involvement of both basal forebrain and brainstem cholinergic nuclei in the latter.

Non-uniformity in the regional pattern of Lewy pathology in brains of dementia with Lewy bodies

We examined the regional pattern of Lewy pathology in brains of dementia with Lewy bodies (DLB) to clarify whether Lewy pathology uniformly progresses or not. Thirty-five autopsied DLB cases were examined using alpha-synuclein-immunohistochemistry, and the regional degree of Lewy pathology in the brainstem, diencephalon and cerebral cortex was quantitatively evaluated. Consequently, we found that the regional pattern of Lewy pathology differed according to the pathological subtype, and was divided into three types: type 1 showed a brainstem-predominant pattern, type 2 was almost equal for the brainstem and cerebral cortex, and type 3 showed a cerebral cortex-predominant pattern. The limbic type/pure and common forms were mainly composed of type 1, whereas the neocortical type/common and Alzheimer's disease (AD) forms were mainly composed of type 3. These findings suggest the possibility that Lewy pathology of the limbic type/pure and common forms mainly progresses from the brainstem to the cerebrum, whereas that of the neocortical type/common and AD forms mainly progresses from the cerebrum to the brainstem. Cases with type 1 Lewy pathology mainly developed parkinsonism, whereas those with type 3 Lewy pathology mainly developed dementia. This corresponded to most of the limbic type/ pure and common forms which developed parkinsonism, whereas most of the neocortical type/common and AD forms developed dementia. Type 1 cases may thus be clinically diagnosed as having Parkinson's disease (PD) with dementia. These findings suggest that PD has clinico-pathological continuity with DLB, and that the regional pattern of Lewy pathology is not uniform.

Expression of cellular prion protein in the frontal and occipital lobe in Alzheimer's disease, diffuse Lewy body disease, and in normal brain: an immunohistochemical study

Cellular prion protein (PrP(c)) is a glycoprotein expressed at low to moderate levels within the nervous system. Recent studies suggest that PrP(c) may possess neuroprotective functions and that its expression is upregulated in certain neurodegenerative disorders. We investigated whether PrP(c) expression is altered in the frontal and occipital cortex in two well-characterized neurodegenerative disorders--Alzheimer's disease (AD) and diffuse Lewy body disease (DLBD)--compared with that in normal human brain using immunohistochemistry and computerized image analysis. The distribution of PrP(c) was further tested for correlation with glial reactivity. We found that PrP(c) was localized mainly in the gray matter (predominantly in neurons) and expressed at higher levels within the occipital cortex in the normal human brain. Image analysis revealed no significant variability in PrP(c) expression between DLBD and control cases. However, blood vessels within the white matter of DLBD cases showed immunoreactivity to PrP(c). By contrast, this protein was differentially expressed in the frontal and occipital cortex of AD cases; it was markedly overexpressed in the former and significantly reduced in the latter. Epitope specificity of antibodies appeared important when detecting PrP(c). The distribution of PrP(c) did not correlate with glial immunoreactivity. In conclusion, this study supports the proposal that regional changes in expression of PrP(c) may occur in certain neurodegenerative disorders such as AD, but not in other disorders such as DLBD.

A comparison of episodic memory deficits in neuropathologically-confirmed Dementia with Lewy bodies and Alzheimer's disease

Little is known about possible differences in the memory deficits that occur in Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD). We compared 24 autopsy-confirmed DLB and 24 age-, education-, and MMSE-matched autopsy-confirmed AD patients on the California Verbal Learning Test (CVLT) and the Wechsler Memory Scale-Revised Logical Memory subtest. The DLB and AD groups were similarly impaired on CVLT Total Learning (Trials 15) and Long Delayed Free Recall, but the DLB group demonstrated relative improvement in Savings scores and on recognition testing compared to the AD group. Likewise, the patient groups were equally impaired on Logical Memory immediate and delayed recall, but the DLB group's Saving scores were significantly better than those of the AD patients. These results indicate that while both DLB and AD patients exhibit significant memory impairment, the ability to consolidate information may be less severely impaired in DLB patients than in AD patients.

α-Synuclein: Normal Function and Role in Neurodegenerative Diseases

Synucleins are a family of small, highly charged proteins expressed predominantly in neurons. Since their discovery and characterization during the last decade, much has been learned about their structure, potential functions, interactions with other proteins, and roles in disease. One of these proteins, alpha-synuclein (alpha-syn), is the major building block of pathological inclusions that characterize many neurodegenerative disorders, including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and neurodegeneration with brain iron accumulation type 1 (NBIA-1), which collectively are termed synucleinopathies. Furthermore, genetic and biological studies support a role for alpha-syn in the pathophysiology of these diseases. Therefore, research must be continued in order to better understand the functions of the synuclein proteins under normal physiological conditions as well as their role in diseases.

Neuroimaging in dementia with Lewy bodies: metabolism, neurochemistry, and morphology

Dementia with Lewy bodies (DLB) is recognized as one of the most common forms of neurodegenerative dementia. Neuroimaging contributes to a better understanding of the pathophysiology of DLB by examining alterations in brain metabolism, neurochemisty, and morphology in living patients. Neuroimaging can provide objective and quantifiable antemortem markers for the presence of and the progression of DLB and permits differentiation from other dementias. This article reviews current neuroimaging findings in DLB with particular attention to occipital hypometabolism, dopaminergic and cholinergic deficits, and medial temporal lobe atrophy as measured by positron emission tomography, single-photon emission computed tomography, and magnetic resonance imaging.

Dementia with Lewy bodies: neuropathology

The pathologic substrate of the clinical syndrome of dementia with Lewy bodies (DLB) remains to be determined. Only a few prospective clinicopathologic studies have been reported. In those reports, most cases of DLB had neocortical or limbic Lewy bodies and Alzheimer-type pathology below threshold for diagnosis of Alzheimer's disease. These results are in accord with recent retrospective clinicopathologic studies of dementia occurring in Parkinson's disease, in which cortical Lewy bodies, rather than concurrent Alzheimer's disease, are increasingly recognized as the pathologic substrate of dementia. Additional clinicopathologic studies are warranted to address the role of other Lewy-related pathology, most notably Lewy neurites, in the cognitive impairment of DLB.

Regional distribution of alpha-synuclein pathology in unimpaired aging and Alzheimer disease

The amygdaloid complex (AC) was found highly vulnerable to alpha-synuclein (alphaS) pathology in both familial and sporadic Alzheimer disease (AD), and recently, incidental Lewy bodies (LBs) were identified primarily in the lower brainstem. This challenges the traditional view that the substantia nigra (SN) is the region that is predominately affected in the spectrum of LB disorders. We examined the immunoreactivity of alphaS in the SN, the nucleus basalis of Meynert (nbM), and the AC in 904 subjects with or without concomitant AD pathology. AlphaS-positive structures were seen in at least one of the studied brain areas in 121 subjects (13%). The affected regions in the alphaS-positive subjects included the SN (89%), the nbM (73%), and the AC (67%). This study also included 82 sporadic AD patients diagnosed using CERAD criteria. AlphaS-positive structures were seen in 32% of the AD patients, with the SN and AC being equally affected. In a few subjects the AC was the only affected area. However, this was not inevitably associated with AD pathology, but was related to cognitive decline. Incidental LBs in the SN were described in the occasional subjects, with no alphaS pathology in the lower brainstem.

Immunohistochemical study of the expression of cytokines and nitric oxide synthases in brains of patients with dementia with Lewy bodies

Regional expression of cytokines (IL-1alpha, TNF-alpha), inducible nitric oxide synthase (iNOS) and neuronal NOS (nNOS) was immunohistochemically investigated in the brains of patients with dementia with Lewy bodies (DLB), compared with those of patients with Alzheimer's disease (AD) and non-demented elderly persons. It has been reported that inflammatory responses by cytokines and oxygen free radicals such as nitric oxide (NO) are associated with damaged neurons, degenerative neurites or amyloid deposits in AD brains. In the present study, overexpression of IL-1alpha, TNF-alpha and iNOS was demonstrated in the amygdala, hippocampus, entorhinal and insular cortices of DLB brains, which are pathologically the most vulnerable regions in DLB brains as well as AD brains. In addition, some Lewy body (LB)-bearing neurons were involved by the processes of IL-1alpha- and TNF-alpha-positive microglia, and most extracellular LB were associated with the processes of TNF-alpha- and iNOS-positive astroglia. Glial involvement was also found around neuritic plaques and extracellular neurofibrillary tangles. In contrast, the expression of nNOS was reduced in the amygdala of DLB brains showing severe Lewy pathology. These findings suggest that cytokines and NO are significantly implicated in neuronal damage and death including LB formation in DLB brains.

Loss of response to levodopa in Parkinson's disease and co-occurrence with dementia: role of D3 and not D2 receptors

Previous data suggest a relationship between the loss of response to levodopa in Parkinson's disease (PD) patients with the co-occurrence of dementia, but the role of alterations in the dopamine system has not been explored. We measured the extent of striatal DA loss and changes in striatal DA D(2) and D(3) receptors in postmortem striatum of PD patients who historically had or had not lost their clinical response to dopaminergic drugs and/or had an additional diagnosis of dementia. Clinical evaluation and retrospective chart reviews for PD and dementia, and neuropathological diagnoses were obtained. All PD cases (+/-dementia), regardless of response to dopaminergic drugs, exhibited a significant and similar degree and pattern of loss of tyrosine hydroxylase immunocytochemistry and DA transporter binding in striatum, and loss of tyrosine hydroxylase-immunoreactive neurons and brain-derived neurotrophic-immunoreactive neurons from the ventral midbrain. D(2) receptor concentrations were modestly elevated in the rostral striatum of all the PD cases (+/-dementia), whether or not they continued to respond to dopaminergic drugs. In contrast, loss of D(3) receptor concentration correlated with loss of response to dopaminergic drugs, independent of the presence or absence of dementia. A maintained response to dopaminergic drugs correlated with an elevation of D(3) receptors. Dementia with PD was highly correlated with a loss of response to dopaminergic drugs, and was also correlated with reduced D(3) receptors. The alterations in D(3) receptor concentrations were greatest in the nucleus accumbens, caudal striatum, and globus pallidus. Thus, loss of dopamine D(3) receptors may be a more important contributing factor to a loss of response to dopaminergic drugs than changes in the D(2) receptor.

Clinical correlates of selective pathology in the amygdala of patients with Parkinson's disease

The amygdala exhibits significant pathological changes in Parkinson's disease, including atrophy and Lewy body (LB) formation. Amygdala pathology has been suggested to contribute to some clinical features of Parkinson's disease, including deficits of olfaction and facial expression. The degree of neuronal loss in amygdala subnuclei and the relationship with LB formation in non-demented Parkinson's disease cases have not been examined previously. Using stereological methods, the volume of neurones and the number of neurones in amygdala subdivisions were estimated in 18 prospectively studied, non-demented patients with Parkinson's disease and 16 age- and sex-matched controls. Careful exclusion (all cortical disease) and inclusion (non-demented, levodopa-responsive, idiopathic Parkinson's disease or controls) criteria were applied. Seven Parkinson's disease cases experienced well-formed visual hallucinations many years after disease onset, while nine Parkinson's disease cases and three controls were treated for depression. Anatomically, the amygdala was subdivided into the lateral nucleus, the basal (basolateral and basomedial) nuclei and the corticomedial (central, medial and cortical nuclei) complex. LB and Lewy neurites were identified by immunohistochemistry for alpha-synuclein and ubiquitin and were assessed semiquantitatively. LB were found throughout the amygdala in Parkinson's disease, being present in approximately 4% of neurones. Total amygdala volume was reduced by 20% in Parkinson's disease (P = 0.02) and LB concentrated in the cortical and basolateral nuclei. Lewy neurites were present in most cases but did not correlate with any structural or functional variable. Amygdala volume loss was largely due to a 30% reduction in volume (P = 0.01) and the total estimated number of neurones (P = 0.007) in the corticomedial complex. The degree of neurone loss and the proportion of LB-containing neurones in the cortical nucleus within this complex were constant across Parkinson's disease cases and neither variable was related to disease duration (R(2 )< 0.03; P > 0.5). The cortical nucleus has major olfactory connections and its degeneration is likely to contribute to the early selective anosmia common in Parkinson's disease. There was a small reduction in neuronal density in the basolateral nucleus in all Parkinson's disease cases, but no consistent volume or cell loss within this region. However, the proportion of LB-containing neurones in the basolateral nucleus was nearly doubled in cases that exhibited visual hallucinations, suggesting that neuronal dysfunction in this nucleus contributes to this late clinical feature. Detailed quantitation of the other amygdala subdivisions failed to reveal any other substantial anomalies or any associations with depression. Thus, the impact of Parkinson's disease on the amygdala is highly selective and correlates with both early and late clinical features.

Progression and staging of Lewy pathology in brains from patients with dementia with Lewy bodies

Using alpha-synuclein-immunohistochemistry, 27 brains of dementia with Lewy bodies (DLB) were investigated to identify the progression of Lewy pathology including Lewy bodies (LB) and LB-related neurites in the cerebrum. The numbers of alpha-synuclein-positive LB and LB-related neurites were semiquantitatively evaluated in the amygdala, hippocampus, entorhinal cortex, transentorhinal cortex, insular cortex, middle temporal cortex and superior frontal cortex. The results indicated that Lewy pathology within the neuron progresses first in the axonal terminal, subsequently in the cell body and finally in the dendrite, that Lewy pathology in the cerebral cortex progresses first in layers V-VI, subsequently in layer III and finally in layer II, and that Lewy pathology in the cerebrum progresses first in the amygdala, subsequently in the limbic cortex and finally in the neocortex. In addition, Lewy pathology was graded from stage I to stage IV based on the progression of Lewy pathology. The 27 brains examined were classified into 3 brains showing stage I, 11 showing stage II, 7 showing stage III and 6 showing stage IV. Comparing these stages with the pathological subtypes of DLB brains, brains of the subtype showing severe Alzheimer pathology corresponded to brains showing an advanced stage, suggesting that Alzheimer pathology exacerbates Lewy pathology.

Relationship in the formation process between neurofibrillary tangles and Lewy bodies in the hippocampus of dementia with Lewy bodies brains

Using tau immunohistochemistry and alpha-synuclein immunohistochemistry, we quantitatively investigated the most frequent sites and the formation process of neurofibrillary tangles (NFT) and Lewy bodies (LB) in the hippocampus from 20 patients with dementia with Lewy bodies (DLB). NFT were most frequently found in the CA2 and the subiculum-pre-CA1, while LB were most frequently found in the CA3-4 and the subiculum-pre-CA1. In the intrahippocampal routes of the perforant pathway, tau immunoelectron microscopy demonstrated distal axons containing aggregated tau-positive microtubules, while alpha-synuclein immunoelectron microscopy revealed terminal axons containing aggregated alpha-synuclein-positive tubular or filamentous components. These findings suggest that NFT and LB are first formed in the CA2 and the CA3-4 related to degeneration of the nonperforating route of the perforant pathway, respectively, and subsequently in the subiculum-pre-CA1 chiefly related to degeneration of the perforating route. Coexistence of NFT and LB in the same neurons was found most frequently in the subiculum-pre-CA1. In addition, coexistence of tau and alpha-synuclein was found in terminal axons of the perforant pathway, and tau accumulated not in paired helical filaments but in the periphery of alpha-synuclein-positive components immunoelectron-microscopically, suggesting that alpha-synuclein stimulates the accumulation of phosphorylated tau in terminal axons.

Frequency and distribution of TUNEL-positive neurons in brains of dementia with Lewy bodies: comparison with those in brains of Alzheimer's disease

The present study investigated the frequency and distribution of TUNEL-positive neurons in brains of dementia with Lewy bodies (DLB) in comparison with those in brains of Alzheimer's disease (AD), Down syndrome (DS) and non-demented elderly persons. In DLB brains, TUNEL-positive neurons were increased in frequency compared with those in non-demented elderly brains, and showed a distribution similar to those in AD and DS brains. DLB cases with TUNEL-positive neurons showing severe Lewy pathology were all neocortical type, while DLB cases of the limbic type showing mild Lewy pathology did not demonstrate TUNEL-positive neurons. In addition, we investigated the relationships between TUNEL-positive neurons and pathological hallmarks of DLB or AD brains. TUNEL-positive neurons had no Lewy bodies or neurofibrillary tangles, and were not located within amyloid deposits. These findings suggest that neuronal damage showing DNA fragmentations occurs in DLB brains as well as in AD and DS brains, and that it is accelerated by progression of Lewy pathology as well as Alzheimer pathology, although it is not directly related to their pathological hallmarks.

Alzheimer's disease versus dementia with Lewy bodies: cerebral metabolic distinction with autopsy confirmation

Seeking antemortem markers to distinguish Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), we examined brain glucose metabolism of DLB and AD. Eleven DLB patients (7 Lewy body variant of AD [LBVAD] and 4 pure diffuse Lewy body disease [DLBD]) who had antemortem position emission tomography imaging and autopsy confirmation were compared to 10 autopsy-confirmed pure AD patients. In addition, 53 patients with clinically-diagnosed probable AD, 13 of whom later fulfilled clinical diagnoses of DLB, were examined. Autopsy-confirmed AD and DLB patients showed significant metabolic reductions involving parietotemporal association, posterior cingulate, and frontal association cortices. Only DLB patients showed significant metabolic reductions in the occipital cortex, particularly in the primary visual cortex (LBVAD -23% and DLBD -29% vs AD -8%), which distinguished DLB versus AD with 90% sensitivity and 80% specificity. Multivariate analysis revealed that occipital metabolic changes in DLB were independent from those in the adjacent parietotemporal cortices. Analysis of clinically diagnosed probable AD patients showed a significantly higher frequency of primary visual metabolic reduction among patients who fulfilled later dinical criteria for DLB. In these patients, occipital hypometabolism preceded some clinical features of DLB. Occipital hypometabolism is a potential antemortem marker to distinguish DLB versus AD.

A neuropathological study of the disturbance of the nigro-amygdaloid connections in brains from patients with dementia with Lewy bodies

We neuropathologically and immunohistochemically investigated characteristics of the central amygdaloid nucleus lesion and its relationship with the substantia nigra lesion in dementia with Lewy bodies (DLB) brains. Nine DLB, four Parkinson's disease (PD) and four Alzheimer-type dementia (ATD) cases were examined. The degree of neuronal loss in the substantia nigra was (+)-(+++) in DLB cases, (+++) in PD cases and (+) in ATD cases. All DLB cases showed spongy change and ubiquitin-positive spheroids in the central nucleus. The degree of spongy change was (+)-(+++) in DLB cases, (+) in PD cases and (-)-(+) in ATD cases, which was correlated with the degree of neuronal loss in the substantia nigra in DLB cases. The number of ubiquitin-positive spheroids was parallel to the degree of spongy change. The central nucleus receives dense dopaminergic fibers from the substantia nigra. Many ubiquitin-positive spheroids were also positive to alpha-synuclein and tyrosine-hydroxylase, suggesting that they derive from the degeneration of terminal or distal axons of Lewy body-bearing dopaminergic neurons in the substantia nigra. The disturbance of the dopaminergic connections from the substantia nigra to the central nucleus may be responsible for psychotic symptoms in DLB patients.

Glial involvement in the degeneration process of Lewy body-bearing neurons and the degradation process of Lewy bodies in brains of dementia with Lewy bodies

Glial involvement in the degeneration process of Lewy body (LB)-bearing neurons and the degradation process of LBs in the cerebral cortex and amygdala in brains of dementia with Lewy bodies was investigated immunohistochemically. HLA-DR-positive microglia frequently extended their processes to degenerated neurons with alpha-synuclein-positive LBs, while some GFAP-positive astroglial processes attached to weakly alpha-synuclein-positive extracellular LBs. Some intracellular LBs were immunoreactive to anti-C4d antibody, and these LB-bearing neurons were involved by activated microglia. About half of the intracellular LBs were immunoreactive to anti-chromogranin-A (CGA) antibody, and most of CGA-positive LB-bearing neurons were surrounded by microglia. Although we could find no evident participation of TNF-alpha, a candidate cytokine that is up-regulated by microglia following CGA stimulation, in the degeneration process of LB-bearing neurons, some intracellular LBs were immunoreactive to the antibody to NF-kappaB, a transcriptional factor activated by cytokines. These findings suggest that microglia participate in the degeneration process of LB-bearing neurons via varying immunogenic elements including complement proteins, CGA and probably some cytokines, and that astroglia participate in the degradation process of LBs.

Alpha-synuclein-positive structures in cases with sporadic Alzheimer's disease: morphology and its relationship to tau aggregation

Alzheimer's disease (AD) and Parkinson's disease share common clinical and pathological features. In this study, we examined the relationship between AD pathology and alpha-synuclein aggregation. The frequency and distribution of alpha-synuclein-positive structures were systematically investigated in 27 cases with sporadic AD by alpha-synuclein immuno-histochemistry. Thirteen (48.2%) of 27 cases had various alpha-synuclein-positive structures as well as Lewy bodies. The frequency and density of senile plaques and neurofibrillary tangles were not significantly different between cases with alpha-synuclein structures and those without. alpha-Synuclein-positive structures were found most frequently in the amygdala. The alpha-synuclein-positive inclusions that are different from Lewy bodies were observed at the highest rate in the hippocampus. The discovery of alpha-synuclein as the constituent of Lewy bodies facilitated the detection of Lewy-related structures even in AD cases with widespread and numerous neurofibrillary tangles. alpha-Synuclein-positive inclusions except for Lewy bodies are exposed, and the distribution of them indicates that Lewy body formation may be influenced by the degree of tau aggregation. This study also supports the suggestion that cases with AD pathology can be classified into two groups according to the existence or absence of alpha-synuclein aggregation.

Glucose hypometabolism and neuropathological correlates in brains of dementia with Lewy bodies

Cerebral glucose metabolism using positron emission tomography (PET) with (18)F-fluorodeoxyglucose was examined in 11 patients with probable Alzheimer's disease (AD), 6 patients with probable, and 1 patient with autopsy-confirmed dementia with Lewy bodies (DLB) as well as in 10 age-matched normal control subjects. Among widespread cortical regions showing glucose hypometabolism in the DLB group, the metabolic reduction was most pronounced in the visual association cortex compared to that in the AD group. Using a metabolic ratio of 0.92 in the visual association cortex as a cutoff (mean-2 SD of normal control subjects), DLB could be distinguished from AD with a sensitivity of 86% and a specificity of 91%. In contrast, apolipoprotein E4 allele frequency and cerebrospinal fluid tau levels did not differ significantly between the two groups. In order to further dissect out neuropathological correlates of the dysfunctional occipital lobe, postmortem brains from 19 patients with AD and 17 with DLB as well as 11 brains from normal controls were examined. A distinct and extensive spongiform change with coexisting gliosis was variably noted throughout cerebral white matter with relative sparing of gray matter in DLB. Notably, the white matter spongiform change and gliosis was most prominently and consistently found in the occipital region of DLB, and the severity of the spongiform change in each brain region generally paralleled to the regional difference in reduced glucose metabolism between the living AD and DLB patients. These findings suggest that (1) among several potential antemortem biomarkers in the diagnosis of DLB, measures of the glucose metabolism in the occipital cortex may be an informative diagnostic aid to distinguish DLB from AD; and (2) a pathological process that generates widespread spongiform change and gliosis in long projection fibers may contribute, at least in part, to the characteristic imaging features of DLB.

Occurrence of human alpha-synuclein immunoreactive neurons with neurofibrillary tangle formation in the limbic areas of patients with Alzheimer's disease

We examined alpha-synuclein immunoreactivity in the brains from 23 patients with Alzheimer's disease (AD) and two patients with Down's syndrome. In ten of the 23 AD cases and both the two Down's syndrome cases, alpha-synuclein immunoreactivities were observed in the neurons of the limbic areas, predominantly of the amygdala. Nearly all alpha-synuclein-positive neurons had tau-positive neurofibrillary tangles (NFT) in the same neurons, and these consisted of intermingled-type and superimposed-type. By immunoelectron microscopy, the intermingled-type revealed aggregations of alpha-synuclein-positive filamentous components, which were in continuity with paired helical filaments (PHF), while the superimposed-type revealed accumulations of alpha-synuclein-positive non-filamentous components in PHF bundles. These findings suggest that alpha-synuclein can accumulate in PHF and form filamentous aggregations in neurons of the limbic areas in AD cases.

Laminar distribution of pick bodies, pick cells and Alzheimer disease pathology in the frontal and temporal cortex in Pick's disease

Lesions in Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) have distinct laminar distributions in the cortex. The objective of the present study was to test the hypothesis that the lesions characteristic of Pick's disease (PD) and AD have distinctly different laminar distributions in cases of PD. Hence, the laminar distribution of Pick bodies (PB), Pick cells (PC), senile plaques (SP) and neurofibrillary tangles (NFT) was studied in the frontal and temporal cortex in nine patients with PD. In 57% of analyses of individual cortical areas, the density of PB was maximal in the upper cortex while in 25% of analyses, the distribution of PB was bimodal with density peaks in the upper and lower cortex. The density of PC was maximal in the lower cortex in 77% of analyses while a bimodal distribution was present in 5% of analyses. The density of NFT was maximal in the upper cortex in 50% of analyses, in the lower cortex in 15% of analyses, with a bimodal distribution in 4% of analyses. The density of SP did not vary significantly with cortical depth in 86% of analyses. The vertical densities of PB and PC were negatively correlated in 12/21 (57%) of brain areas. The maximum density of PB in the upper cortex was positively correlated with the maximum density of PC in the lower cortex. In 17/25 (68%) of brain areas, there was no significant correlation between the vertical densities of PB and NFT. The data suggest that the pathogenesis of PB may be related to that of the PC. In addition, although in many areas PB and NFT occur predominantly in the upper cortex, the two lesions appeared to affect different neuronal populations.

Frequent coexistence of Lewy bodies and neurofibrillary tangles in the same neurons of patients with diffuse Lewy body disease

We examined the frequency of neurons with coexistent Lewy bodies (LB) and neurofibrillary tangles (NFT) in diffuse Lewy body disease brains, by a double-immunostaining method using MDV2 and Human tau. Double-positive neurons were frequently observed in the limbic areas. These neurons mostly revealed the feature of intermingled MDV2- and Human tau-positive substances. Immunoelectron microscopically, the MDV2-positive components were not in continuity with the MDV2-negative paired helical filaments (PHF). The MDV2-positive LB were surrounded by the small PHF bundles, frequently accompanied by the randomly oriented PHF within LB. In the intermingled neurons, MDV2-positive non-filamentous components without LB were found among the large PHF bundles. These non-filamentous components may represent the early stage of LB formation.

Antibodies to alpha-synuclein detect Lewy bodies in many Down's syndrome brains with Alzheimer's disease

Immunohistochemical examination of 20 Down's syndrome brains, using antibodies to alpha-, beta-, and gamma-synuclein, demonstrated many alpha-synuclein-positive Lewy bodies and dystrophic neurites in 50% of amygdala samples from Down's syndrome brains with Alzheimer's disease. Similar lesions were less common in other regions of these brains, none of which contained beta-synuclein or gamma-synuclein abnormalities. Thus, alpha-synuclein-positive Lewy bodies and neuritic processes frequently occur with Alzheimer's disease in Down's syndrome brains.

Dementia with Lewy bodies

In the last decade, a new degenerative dementia, probably the second most common after Alzheimer's disease (AD), has been increasingly recognized under the consensus name of dementia with Lewy bodies (DLB). This article reviews current clinical, genetic, and pathological DLB data and indicates directions for future research. DLB overlaps in clinical, pathological, and genetic features with AD and Parkinson's disease (PD). Clinically, it is characterized by progressive cognitive impairment with significant fluctuations in alertness, parkinsonism, and psychosis with recurrent hallucinations. The neuropathological hallmarks are the intracytoplasmic inclusions in substantia nigra typical of PD, known as Lewy bodies (LB) but distributed widely throughout paralimbic and neocortical regions. Most of the cases also coexist with a plaque predominant AD. It is probably the unique and differential distribution of the lesions throughout cortical and subcortical structures in each of these disorders that supports a specific clinical syndrome and may ultimately prove most useful in understanding their different etiologies. Several genes have recently been implicated in LB formation. Special interest arises from mutations in the alpha-synuclein gene, which appears to be responsible for autosomal dominant PD in several kindreds. This gene encodes a presynaptic protein, a fragment of which is present in AD plaques. Recent studies show intense and quite specific alpha-synuclein immunoreactivity in LB and related neurites, suggesting a potential role of this protein in the aggregation or precipitation of LB inclusions.

Simplified neuropathological diagnosis of dementia with Lewy bodies

Pathological criteria have recently been developed to differentiate those cases where Lewy bodies contribute to the dementing process. We applied consensus criteria to 20 cases with a pathological diagnosis of Alzheimer's disease (all demented) and/or Parkinson's disease (three without dementia) and eight controls. In addition, we applied the criteria to the different cortical layers to determine whether the site of the semiquantification affected the diagnosis. In the parietal lobe, few Lewy bodies were observed, and this region could be excluded. Rare Lewy bodies present in the frontal association cortex in a number of Parkinson's disease cases resulted in their classification as limbic or transitional cases with Lewy bodies. Exclusion of this non-limbic association cortex resulted in many of these cases with rare cortical Lewy bodies being re-classified as having brain stem predominant Lewy bodies, thus improving the diagnostic accuracy of the criteria. Most of these cases were non-demented. No other case was re-classified by excluding these cortical regions from the analysis. Few Lewy bodies were present in cortical layers I and II, and these layers could be excluded from the semiquantitative procedure without change to the overall classification of cases. The occasional presence of possible Lewy bodies in cases with Alzheimer's disease and controls incorrectly classified these cases as having brain stem predominant Lewy body disease, although these cases had no brain stem Lewy bodies. These modifications to the consensus criteria for assessing Lewy body disease (i.e. exclude parietal and frontal lobe, cortical layers I and II, and cases without brain stem Lewy bodies), provide significant time and cost savings for neuropathologists and researchers using this criteria to diagnose and study dementia with Lewy bodies.

Dementia with Lewy bodies. A distinct non-Alzheimer dementia syndrome?

Lewy body formation is central to the pathological phenotype of a spectrum of disorders. The most familiar of these is the extrapyramidal syndrome of idiopathic Lewy-body Parkinson's disease (PD). Studies of dementia in the elderly suggest that another manifestation of Lewy body pathology is equally or more common than Parkinson's disease. This syndrome of Dementia with Lewy bodies (DLB) has been given a number of diagnostic labels and is characterised by dementia, relatively mild parkinsonism, visual hallucinations, and fluctuations in conscious level. Although many of these features can arise in Parkinson's disease, the patients with DLB tend to have early neuropsychiatric features which predominate the clinical picture, and the diagnosis of the syndrome in practice is more concerned with the differential diagnosis of Alzheimer's disease (AD). Distinction from AD has clinical importance because of potentially differing therapeutic implications. Diagnostic guidelines for the clinical diagnosis and pathological evaluation of DLB are reviewed. Research into the disorder has centered around characterising the clinical, neuropsychological, pathological, neurochemical and genetic relationships with Alzheimer's disease on the one hand, and Parkinson's disease on the other. Many cases of DLB have prominent pathological features of AD and there are some shared genetic risk factors. Differences from the pathology of PD are predominantly quantitative rather than qualitative and evidence is discussed which suggests that DLB represents a clinicopathological syndrome within the spectrum of Lewy body disorders. The possibility that the syndrome represents a chance association of PD and AD is not supported by published studies.

The spatial patterns of Lewy bodies, senile plaques, and neurofibrillary tangles in dementia with Lewy bodies

The spatial patterns of Lewy bodies (LB), senile plaques (SP), and neurofibrillary tangles (NFT) were studied in ubiquitin-stained sections of the temporal lobe in cases of dementia with Lewy bodies (DLB), which varied in the degree of associated Alzheimer's disease (AD) pathology. In all patients, LB, SP, and NFT developed in clusters and in a significant proportion of brain areas, the clusters exhibited a regular periodicity parallel to the tissue boundary. In the lateral occipitotemporal gyrus (LOT) and parahippocampal gyrus (PHG), the clusters of LB were larger than those of the SP and NFT but in the hippocampus, clusters of the three lesions were of similar size. Mean cluster size of the LB, SP, and NFT was similar in cases of DLB with and without significant associated AD pathology. LB density was positively correlated with SP and NFT density in 42 and 17% of brain areas analyzed, respectively, while SP and NFT densities were positively correlated in 7% of brain areas. The data suggest that LB in DLB exhibit similar spatial patterns to SP and NFT in AD and that SP and NFT exhibit similar spatial patterns in DLB and AD. In addition, in some instances, clusters of LB appeared to be more closely related spatially to the clusters of SP than to NFT.

beta-Amyloid (A beta) deposition in the medial temporal lobe of patients with dementia with Lewy bodies

The distribution and density of diffuse, primitive and classic beta-amyloid (A beta) deposits in the medial temporal lobe (MTL) was studied in cases of dementia with Lewy bodies (DLB) with and without associated Alzheimer's disease (AD) and 15 cases of sporadic AD. In the 'pure' DLB cases, virtually no A beta deposits were observed in the CA regions of the hippocampus or dentate gyrus whereas deposits were distributed throughout the MTL in DLB/AD and AD cases. Densities of diffuse and primitive A beta deposits were similar in AD and DLB/AD cases but density was significantly reduced in the 'pure' DLB cases. The density of the classic deposits was significantly reduced in DLB cases with or without associated AD compared with AD cases. These results suggest that A beta deposition in the MTL in 'pure' DLB cases is similar to that of elderly non-demented patients while, with the exception of the classic deposits, A beta deposition in DLB/AD cases is similar to that in cases of AD alone.

Dementia with Lewy bodies: clustering of Lewy bodies in human patients

Clustering of Lewy bodies (LB) was studied in four regions of the medial temporal lobe in 12 cases of dementia with LB (DLB). LB exhibited clustering in 67/70 (96%) brain areas analysed. In 34/70 (49%) analyses, LB were present in a single large cluster > or = 6400 microns in diameter, in 33/70 (47%) LB occurred in smaller clusters 200-3200 microns in diameter which exhibited a regular periodicity relative to the tissue boundary and in 3/70 (4%), LB were randomly distributed. A regular pattern of LB clusters was observed equally frequently in the cortex and hippocampus, in upper and lower cortical laminae and in 'pure' cases of DLB with negligible Alzheimer's disease (AD) pathology compared with cases of AD with DLB. In cortical regions, there was no significant correlation between LB cluster size in the upper and lower cortical laminae. The regular periodicity of LB clusters suggests that LB develop in relation to the cells of origin of specific cortico-cortical and cortico-hippocampal projections.